Margaret Thatcher, who died Monday from a stroke at the age of 87, left a lasting impression on the City of London. Her huge program of privatizations that saw household names including British Gas and British Airways floated ushered in an age of equity, transferring power to what Thatcher thought was the more efficient private sector, while her massive reform of the U.K.’s financial markets secured London’s position as an international financial hub and a serious rival to Wall Street.